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As multiple fires shock the state, scientists wonder, what comes next?

Nathanael Massey, E&E reporter
Published: Thursday, June 28, 2012
Correction appended.

Crews battled through the day yesterday to contain a fire on the outskirts of Colorado Springs, Colo., as unyielding heat and ember-carrying winds stoked blazes throughout the Rocky Mountain states and beyond.

The Waldo Canyon fire outside of Colorado Springs exploded over firefighters' containment line Tuesday, inflated by 65-mph winds gusting down through the canyon basin. As of last night, 35,000 people had been evacuated.

As the Waldo Canyon fire lights the horizon in Colorado Springs, Colo., a few drivers begin to evacuate. Photo courtesy of  Flickr.

By that time, the fire had reached some 15,000 acres and remained largely uncontained, damaging many homes in the city's northwest corner. Firefighters were in "triage" mode, bypassing houses that were beyond salvaging and focusing their efforts on infrastructure still under threat.

President Obama is set to visit the city tomorrow to survey the damage. The U.S. Air Force has deployed 25 military helicopters to join the efforts, including the rescue of the Air Force Academy, which is near the blaze.

Meanwhile, similar weather conditions have continued to fan the flames of the High Park fire, 15 miles northwest of Fort Collins, Colo. That fire is now considered the most destructive in the state's history, having consumed more than 250 homes.

The High Park fire has affected some 87,250 acres and is currently 65 percent contained.

Wildfires torched more than 200 square miles and burned dozens of homes in southeast Montana yesterday, forcing evacuations after flames jumped a perimeter line built by firefighters. One blaze, the Ashton fire in the southeast corner of the state, grew to more than 110,000 acres in less than 24 hours.

Smaller but significant fires are burning throughout the Rocky Mountain West, including in Wyoming, Utah and New Mexico.

Expect the unexpected

Fires are an integral part of Western ecology, as natural to the region as spring rains, if slightly less common. But in the southwestern United States, researchers have documented larger, higher-severity fire patches in ponderosa pine forests in certain areas that deviate from historical norms.

In certain circumstances, those high-severity fires can constrain a forest's ability to regenerate, said Craig Allen, a U.S. Geological Survey ecologist based at Bandolier National Monument in northern New Mexico.

"Historically, we can see evidence of much bigger fires in Arizona and New Mexico than those we've seen in the last decade," said Allen. "But they weren't behaving the same way. They weren't killing all the trees."

Mature ponderosa pines -- those roughly 15 years or older -- are thick-barked and capable of resisting the kinds of sporadic surface fires that for millennia rippled through the grassy understories of low-elevation forests of the American West.

The view from space as smoke from wildfires casts a pall over Colorado and New Mexico. Photo courtesy of the National Oceanic and Atmospheric Administration.

Every decade or so, those smaller fires would snake through, eliminating much of the area's ground fuel supply before it could build to dangerous levels. Afterward, the more mature surviving ponderosas would reseed the landscape, and the cycle would begin again.

Nearly a century of fire suppression policies has allowed ground fuels to build and forests to thicken, said Allen. "In the absence of fire, these forests have woodified. Now they can sustain a very different type of fire" that is much deadlier.

"The concern now is that, when the smoke clears, there will be many thousands of acres where there are no trees left," he added. "In Arizona and New Mexico, we are seeing huge treeless patches result from big portions of recent high-severity fire."

For high-elevation species like lodgepole pine or chaparral, that wouldn't be a problem. Such trees rely on periodic, high-intensity burns to clear old growth -- in fact, the seeds of a number of species only open under extreme heat.

But for ponderosa forests, such as those under fire in the High Park and Waldo Canyon areas, a super- fire may mean permanent displacement. With no mature trees left to reseed, they have little chance of regaining their foothold in the region.

"The saddest part of this is that these fires might actually change the face of the landscape," said Max Moritz, a fire specialist based at the University of California, Berkeley's College of Natural Resources. "These [ponderosa] stands might take a long time, or forever, to rebound."

In their place, new species -- faster-growing plants like shrubs or prairie grass -- could take hold, transforming hard-hit patches of the Colorado Rockies from forests to grasslands.

Turning up the heat

There are many reasons for the severity of the recent fires in the Southwest, with pine beetles, pollution and weeks of punishing heat all playing exacerbating roles. But from a big-picture perspective, the current conditions are primarily due to a convergence of two factors, said Allen: climate change and land-use history.

The first major disruption to Western fire cycles came in the late 1800s and early 1900s, he said, when cattle and sheep began to graze in large numbers in the region. This depleted the ground fuel supply and allowed forests to thicken.

Then, after a major fire year in 1910, U.S. forest policy took a definitive turn, focusing heavily on suppressing fires before they could spread. Out of this movement came Smokey Bear and his zero- tolerance policy for unattended campfires. And in time, out, too, came a profusion of new fuel.

In the 1970s, the United States headed into a period of longer, wetter winters. Heavy snowfall kept the forests moist and the fires suppressed -- at least for a while.

"In 1996, the Southwest entered a dry period, which emerged into a full-fledged drought in the early 2000s," Allen said. "Winter began ending sooner, and the fires came earlier in the year."

In the Southwest, since the early 1900s, when it began keeping records, "the levels of drought and heat- induced mortality of the past decade have been unprecedented," he said.

Over the past 10 years, North America has set twice as many records for heat as for cold. So far this year, that ratio has been a staggering 9-to-1.

High temperatures and drought weaken trees, making them more susceptible to pine beetle outbreaks, Allen said.

"Trees have thresholds of mortality," he said. "Even without fire or bark beetles, we're starting to see some forest regions being pushed across that threshold."

That makes it increasingly important to engage seriously in proactive, rather than reactive, action to mitigate fires, he said. Prescribed burning, ground-cover clearing and manual thinning of forests are all viable options, if society is willing to designate the necessary resources, he said.

"In the long run, it's less costly than fighting fires after they've broken out," he added.

Correction: An earlier version of this story mistakenly associated Craig Allen's comments about historical fire regimes with the ponderosa pine forests of the Colorado Front Range. Allen's comments pertain to
the southwestern United States, his area of expertise.

Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500


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Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.

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